1. Field of the Invention
This invention relates to radiation detectors and, more specifically, to semiconductor-based radiation detectors.
2. Prior Art
There exist radiation detectors comprising a semiconductor substrate which is of a single-crystal material, an amorphous semiconductor layer of large specific resistance formed on one surface of the substrate, a first electrode formed on the amorphous layer, a second electrode formed on the side of the substrate opposite that on which the amorphous layer has been deposited, and a heterojunction formed between the substrate and the amorphous layer, the heterojunction being reversedbiased by applying a voltage between the recited electrodes to thereby produce a depletion layer in the substrate, the depletion layer producing carriers when exposed to radiation. Such a detector has been the subject matter of patent applications filed in Japan in 1983 by these inventors. The general configuration of such a detector can be seen in the cross-sectional view provided in FIG. 2, hereof. Unfortunately, such a radiation detector as that shown in FIG. 2 suffers from the problem that they have large electrostatic capacitance (which results in noise generated within the detector) and also suffer from the problem of the difficulty of coupling them to preamplifiers.
As a result, a very expensive pre-amplifier has been needed in the past to sufficiently detect the signal from a prior art radiation detector.
Therefore, it is an object of this invention to provide a semiconductor radiation detector which is free of the problems encountered with prior art semiconductor radiation detectors.
It is a further object of this invention to provide a semiconductor-based radiation detector which exhibits minimal electrostatic capacitance and, consequently, minimum thermal noise and minimum difficult in coupling an detector to a pre-amplifier.